Lennox MERIT Series Installation Instructions Manual page 19

Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Intake and Exhaust must be same size.
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Number 2" Pipe
Of 90°
Model
Elbows
045
Used
1 63
2 58
3 53
4 48
5 43
6 38
7 33
8 28
9 23
10 18
Number 2" Pipe
Of 90°
Model
Elbows
045
Used
1 63
2 58
3 53
4 48
5 43
6 38
7 33
8 28
9 23
10 18
Maximum Allowable Exhaust Vent Length Using Ventilated Attic or Crawl Space For Intake Air in Feet
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Number 2" Pipe
Of 90°
Model
Elbows
045
Used
1 61
2 56
3 51
4 46
5 41
6 36
7 31
8 26
9 21
10 16
Maximum Allowable Intake or Exhaust Vent Length
Concentric Termination at Elevation 0 - 4500 ft
070 090 045
48 32 95
43 27 90
38 22 85
33 17 80
28 12 75
23 7 70
18 2 65
13 60
8 n/a 55
3 50
Concentric Termination Elevation 4501 - 10,000 ft
070 090 045
48 32 95
43 27 90
38 22 85
33 17 80
28 12 75
23 7 70
18 2 65
13 60
8 n/a 55
3 50
Standard Termination at Elevation 0 - 10,000 ft
070 090 045
46 24 90
41 19 85
36 14 80
31 9 75
26 4 70
21 65
16 60
11 n/a 55
6 50
1 45
TABLE 7 CONT.
2-1/2" Pipe
Model
070 090
95 79
90 74
85 69
80 64
75 59
70 54
65 49
60 44
55 39
50 34
2-1/2" Pipe
Model
070 090
95 79
90 74
85 69
80 64
75 59
70 54
65 49
60 44
55 39
50 34
TABLE 8
2-1/2" Pipe
Model
070 090
90 68
85 63
80 58
75 53
70 48
65 43
60 38
55 33
50 28
45 23
Page 19
3" Pipe
Model
110 045 070
44 111 111
39 106 106
34 101 101
29 96 96
24 91 91
19 86 86
14 81 81
9 76 76
4 71 71
n/a 66 66
3" Pipe
Model
110 045 070
44 111 111
39 106 106
34 101 101
29 96 96
24 91 91
19 86 86
14 81 81
9 76 76
4 71 71
n/a 66 66
3" Pipe
Model
110 045 070
33 108 107
28 103 102
23 98 97
18 93 92
13 88 87
8 81 82
3 78 77
73 72
n/a 68 67
63 62
090
104
99
94
89
84
79
74
69
64
59
090
104
99
94
89
84
79
74
69
64
59
090
88
83
78
73
68
63
58
53
48
43